I'd get the 9 year old a Nexus 7... it beats the iPod in every way unless you just want a smaller/more portable device. (the idea that there are more games/apps for the iPod vs the Nexus is crap.. anything you could want is going to be on both at this point)

The main reason we are embracing the iPod idea specifically is that his Mom and I both have iPhones. The iOS texting over wifi is nice, and allows us to stay in contact with him directly when he is over at friends' houses without having to give him a cell phone. (Something which I plan to fight for a long, long, long time.)